The invention relates to a sequential demultiplexing receiver for a network of interferometer optical sensors using spectrum modulation encoding, which network is illuminated by a light source of short coherence length and in which each sensor subjected to a physical magnitude to be measured generates an optical path length difference that is a function of the value of said magnitude, said optical path length differences and the differences between them being greater than the coherence length of the source.
In the prior art, the receiver associated with such a network of sensors may be an interferometer, e.g. of the Michelson type, which is tuned in succession to each of the sensors in the network so as to enable it to produce an optical path length difference that is substantially equal to the mean value of the optical path length difference of the sensor in question, thereby producing an interferometer signal at the output from the interferometer for application to a photodetector, with the phase thereof being a direct function of the difference between the path length difference in the sensor and the path length difference in the receiver, providing said difference is less than the coherence length of the source. Known techniques of phase modulation in the receiving interferometer and of demodulating the interferometer signal produced thereby make it possible to discover the phase of said signal and thus the optical path length difference in the sensor, thereby making it possible to deduce the value of the physical magnitude to be measured on the basis of prior calibration (the optical path length difference in the receiver being known).
Nevertheless, it is relatively lengthy and difficult to tune the receiving interferometer successively to each of the path length differences generated in the sensors.
Another solution in the prior art consists in providing as many receiving interferometers as there are sensors, and in connecting them to the network of sensors via optical fibers and optical couplers in a star configuration, each receiving interferometer being tuned to a corresponding sensor, thereby making parallel demultiplexing possible of the signals provided by the network of sensors. However, that requires as many receiving interferometers to be provided as there are sensors, thereby increasing the overall cost of the system.